Adventure Time: Fight for Ooo
by IronJew
Summary: After Finn learns that he is the only human remaining, he meets a strange hooded man. Who is this hooded man? And what is his relation to Finn? Finn is in for the fight of his life.
1. Chapter 1

(A/N) Hey! My name is Iron, and this is my first fanfiction! REVIEW! DISCLAIMER: I do not own Adventure Time or any of its characters. Those belong to Pendleton Ward. I do, however, own the story and the antagonist OC, but you'll see who he is later ;) Also has some Final Fantasy themes.

**Chapter 1**

Another day of fighting monsters and saving people made a 14-year-old boy and his sidekick dog tired. Finn was the only remaining human left on the world of Ooo, and he was still coming to terms with that. The thought made him feel lonely. He had many friends, but he still felt alone.

"What's wrong, Finn?" His dog friend, Jake asked.

"Oh, it's nothing. Just thinking." Finn replied.

"You know I'm here for ya, buddy. You can tell me anything!"

"Well," Finn paused, trying to find the right words to say. "I really feel lonely."

"But, I'm right here!"

"Not like that, Jake."

"Oh, you're still bummed about that? Finn, it's hard, I know, but you just have to look past it."

"But, I just can't!" Finn cried. "This really shouldn't be happening! I can't take it anymore!"

Sobbing, Finn ran off. Jake felt bad. Finn had just learned the truth a few days ago. He and Finn had been through a lot together. The Ice King, The Lich, the Wizard Battle. Gosh, it's been so long.

Finn decided the company of Princess Bubblegum would make him feel better. He loved Princess Bubblegum; he wished she were with him, yet he somehow felt like she didn't think of him that way. He shrugged the thought off. And he saw something strange, a man, about the same height as him, wearing what appeared to be a cloak of some kind.

The man looked at him. Finn froze. He felt strange, like he should somehow know this man. The man smiled at him, and disappeared. That shocked him, as he never noticed that kind of magic before. He had seen ice magic, fire magic, and other types of magic, but never teleportation.

He arrived at the castle; the warm toastiness of the graham cracker and gumdrop halls greeted him. Princess Bubblegum was cleaning the main hall, a smile on her face. She noticed Finn and felt adrenaline rush to her cheeks and heart.

She ran to him, and crashed into him. The soft, pink female hugged Finn. Her bubblegum hair always smelled nice, and he loved it. He loved her.

"Finn, it's so good to see you! Is something wrong?" PB asked.

"The Mushroom War." He muttered.

"Oh, I see. I don't know what to say."

"How did it happen?"

"Well, there were two groups fighting each other, and it seem like everything would go out of control, so they launched the Mushroom Bomb, and ended the fighting."

"But it wiped out all the humans."

"Yes, I'm afraid so."

Finn sunk to the ground, tears forming around his eyes. Princess Bubblegum sat down next to him, putting her arm around him. He couldn't help it, that lonely feeling imbued him. What was his family like? His original friends like? The questions made him sadder.

Suddenly, he thought about that hooded man. Finn only got a glimpse of his face, but he could make out his face. The man looked almost like Finn, except a bit older. He had an average build, with noticeable muscles forming on his arms. But what haunted Finn the most was that smile.

That cruel, twisted smile.


	2. Chapter 2

**Chapter 2**

Finn woke up early the next morning. He muttered something about sword training and left. Princess Bubblegum felt worried. She was in love with him, but didn't want to ruin their friendship. She simply sighed and fell asleep.

Finn went to Stock Woods. He felt the sudden urge to learn how to use magic. Luckily, he found a guide to using magic (cleverly titled; _A Beginner's Guide to Casting Magic_), and it showed quite a few simple spells to learn. He tried casting Fire.

That didn't work.

"Darn it!" Finn shouted. He wasn't doing very well with this. He kept trying and trying, but to no avail. He felt some warmth the 10th try, but still nothing.

Suddenly, he heard a whooshing noise. He looked around. Behind him was the hooded man. That same smile still on his face. Yet, somehow, he felt a feeling of friendliness coming from it.

"You can't just force magic out of your hand," the man said. "It's something you feel inside your body. Magic is using your soul to borrow the powers of nature to bend to your will. Here, I'll show you."

And with that, the man lifted his hand, closed his eyes (or so Finn thought), and shouted, "FIRE!"

A flame erupted from his hand, leaving scorch marks on the tree. Finn was amazed, stunned, in fact. The man noticed his amazement and lifted Finn's arm.

"Now, focus your energy to the palm of your hand. When you feel ready, cast the Fire spell."

Finn closed his eyes, feeling energy flow through his body. He could feel his hand warming up. It felt amazing. He then felt ready to cast it.

"FIRE!" Finn shouted. And with that a ball of flame erupted from Finn's hand and hit a tree.

Finn was overjoyed. He finally cast magic, for goodness sake! Oh, wait till he shows Jake…

"Don't get too cocky," the man said. "Magic can and WILL destroy you if you don't control it."

"Gotcha! I'm gonna be smart about this!"

And with that, the man disappeared. Finn silently thanked him for his help. He didn't get his name, though. Oh, well.

•••

Finn returned home, slamming the front door.

"Whoa, Finn!" Jake exclaimed. "What's made you so happy?"

"I can cast magic, Jake!"

"Yeah, right."

"I'm serious!"

"Bro," Jake stopped Finn from nearly exploding with excitement. "Unless you show me, I'm not gonna believe you."

"Alright, then. Let's go outside!"

Finn ran out the door. Jake followed. The warm sun and cool breeze felt good on Jake's coat of fur. The sun was really bright, though. Jake could barely see.

"Alright," Jake said impatiently. "Where's this so-called magic of yours?"

Finn took a calm, deep breath. He pointed his hand to the sky, and focused all of his energy. He felt his hand warm up again, and knew it was time.

"FIRE!"

A huge fireball erupted from Finn's hand, causing him to sink to his knees, panting. This cast was stronger than normal, he could already tell. He looked at Jake's face, to see his reaction.

Jake was stunned.

All of a sudden, a dragon appeared from the sky.

_That's odd, _Finn thought. _There aren't any dragons around here._

Finn drew Demon Sword from out of his backpack. Jake balled his fists and prepared for battle. The dragon flew towards them at a high speed.

Finn readied his sword, and, with the help of Jake launching him, easily dispatched the dragon.

"S-stop…B-Ben…" the dragon said with its final breath.

"Ben?" A confused Jake asked. "Who's Ben?"

"I don't know," Finn replied. "But whoever he is, he's definitely causing trouble somewhere."

Finn and Jake walked home, while the same question pondered their minds.

Who's Ben?

And, what is he doing?


	3. Chapter 3

**Chapter 3**

Finn couldn't shrug off the feeling of the name that dragon said. Ben. Who, or what is Ben? The name sounded so familiar…

"FINN!" Jake shouted. "SNAP OUT OF IT!"

Immediately, Finn gasped and looked around him. The people of Candy Kingdom were there, worried for his safety. Even Marceline was there, and her normal bad girl attitude was replaced with an attitude of worry. Even Ice King was there.

Wait, What?!

"What are you doing here?" Finn shot up and put the Demon Sword to Ice King's neck.

"Finn, stop!" Princess Bubblegum pleaded. He immediately put down his sword in confusion. Why doesn't she want him to defeat Ice King?

"I called him here. We all need to talk about today's events."

Finn realized she was talking about the dragon. He nodded reluctantly and apologized to Ice King.

"Don't sweat it," the old blue king said to him, "Right now is not the time to fight each other."

The meeting went underway. People from the Candy Kingdom were complaining about broken windows and destroyed treasures due to the dragon. Marceline spoke of the dragon flying through the Nightosphere and terrorizing the already terrorized prisoners. Ice King spoke of his penguin friends frozen to the bone in fear.

Finn could care less about what they said. He wanted to know why that dragon appeared in the first place. Then, suddenly, he remembered what the dragon muttered.

"Does anyone know a Ben around here?" Finn shouted at the top of his lungs.

Confused looks went around as the citizens tried, to their fullest extent, to see if they knew a Ben.

"No, I don't think so."

"No."

"I don't think I do."

Marceline even tried to think to see if she knew him.

"No, though it really sounds familiar." She said.

Great. No leads. This will lead them nowhere.

That is, until, he noticed the cloaked man in the crowd. He started feeling all the mixed emotions he normally felt when he saw that mysterious man. The biggest emotion he felt at the moment was anger.

He jumped out of his chair and ran after the mysterious figure. The figure stood there, waiting for Finn to charge after him. He then lifted his hand….

And stopped Finn in his tracks!

"Agh…can't move…why?" Finn tried his absolute hardest to move. He was getting tired.

"I wouldn't move if I were you," that soothing voice from underneath the cloak said, "You wouldn't want to be permanently paralyzed, now, would you?"

The man put his hand down, and suddenly Finn could move again. Finn could barely do so, however, having used up all of his strength trying to move.

"Who are you, kind sir?" asked Princess Bubblegum in her sweet, dulcet tone.

The man slowly lifted up his hood to reveal a boy, only two or three years older than Finn. He looked like Finn as well, though with brown hair, and his build was slightly larger. He had beautiful brown eyes that looked at everyone with a sense of peace.

"Why, I'm Finn's dear older brother. His real brother. My name is Ben. Nice to meet you."


	4. Chapter 4

**Chapter 4**

Everyone had a look of fear on their faces. Jake was completely shocked. Princess Bubblegum was just as shocked. Even Marceline and the Ice King were shocked.

Everyone looked to Finn.

He couldn't believe what he was hearing. He had a brother? A real one, not just Jake? He looked up at Ben, and could feel tears forming in his eyes.

"Why does everyone look so scared?" Ben asked. "I'm not here to kill anyone, I just came to say hello."

"Finn," Jake said with increasing worry, "I don't know if he's lying or not, I can't tell."

"Oh, don't worry, Jake. I'm not lying. I've been looking for my dear younger brother for years now. Who would've thought it would be Princess Bubblegum's Candy Kingdom?"

Ben walked over to the fair princess and knelt down. Finn couldn't believe it. His own brother, a gentleman!

"Your Highness," Ben said in a way a knight would, "I thank you for caring for my brother. He seems to have many friends in this wonderful kingdom."

"My p-pleasure." She said hesitantly.

Finn walked over to his brother. Ben, huh? He walked closer, and hugged him.

He could feel tears rushing down his face. He had never been so happy in his life.

"It's good to see you too, Finn." His brother remarked. "Now, Finn, I'm starving. What is there to eat around here?"

Everyone couldn't help but giggle. He sure was Finn's brother, all right.

"What? What's so funny?" Ben looked around, confused.

"Come," Princess Bubblegum announced, "A grand feast is in store, for we have found another living human!"

Everyone cheered. Jake walked up to Finn and his brother. He was happy to see them reunited, but there was something wrong. He could feel it in his gut. He shook off the feeling.

Ben ate a lot of food. He almost cleared out the castle of its food supply. He said it was because he barely ate searching for Finn.

"That reminds me," Finn said, "Why were you searching for me in the first place?"

"Oh, boy," Ben said, "This is gonna be good. You might want to hold on to your chair for this, cause it's quite the doozy."

Finn prepared himself.

"The Great Mushroom War," Ben began, "Was a very violent, very long battle. Humans fought over resources they found very valuable, such as diamonds, or oil. The fight turned sour, and eventually every world power turned to using nuclear weapons to solve the conflict. Almost every human was destroyed, except for some. A lot of things were mutated, creating human-like inanimate objects. Our parents were trying to care for both of us, you were only a baby, so you probably wouldn't remember any of it. I was 4 at the time, so I knew what was happening around me. We were resting near a junkyard, when all of a sudden we were jumped by a group of thugs. They wanted all of our stuff, but our dad was a good fighter. He didn't survive for very long, and was killed by a knife to his back. The goons noticed Mom with you in her hands, and thought you were food. They killed Mom, and went after you. I didn't want you to die, but I was powerless. Someone shouted and distracted them, and a little girl came up to me with a black orb in her hands. She told me to touch it if I wanted to protect you, so I did. I felt something enter my body, and it made me stronger. It was a demon's spirit, but the demon was one that was not bloodthirsty. I killed all of the goons with my magical powers that he gave me, except for one. She ran off with you, though she didn't get very far, she ended up dying before she got a chance to eat you. That's when Jake's mom and dad found you. I vowed to train myself to control the demon inside of me, and to search for you."

Finn was shocked. That all happened?

"But," Ben said. "I ended up figuring out who were the people that helped me. Do you want to know who they are?"

Finn nodded with excitement.

"It was none other than….. Ice King and Marceline."


End file.
